| onda ögat | evil eye |
| Ondangwa | Ondangwa |
| Ondes Martenot | Ondes Martenot |
| Ondo | Ondo State |
| ondska | evil |
| Ondskans axelmakter | Axis of evil |
| Ondskans blommor | Les Fleurs du mal |
| Ondskans hus | The People Under the Stairs |
| Ondskans imperium | Evil empire |
| ondskefull | mean |
| ondskefullt | diabolically |
| Ondskefullt geni | Evil genius |
| One Day in Your Life | One Day in Your Life |
| One Penny Black | Penny Black |
| One Piece | One Piece |
| One Step Beyond | One Step Beyond |
| One Tree Hill | One Tree Hill |
| Onedinlinjen | The Onedin Line |
| Onega | Lake Onega |
| Oneida County | Oneida County |
| onekligen | undeniable |
| Oneliner | One-liner joke |
| Onesilos | Onesilus |
| Onesimos | Onesimus |
| Oneworld | Oneworld |
| Oni | Oni |
| Onion routing | Onion routing |
| onkel | uncle |
| Onkel Toms Hütte | Onkel Toms Hütte |
| Onkel Toms stuga | Uncle Tom Cabin |
| Onkel Vanja | Uncle Vanya |
| onkologi | oncology |
| Onnens | Onnens |
| Ono | Ono Island |
| Onomastik | Onomastics |
| onomatopoesi | onomatopoeia |
| onormal | deviant |
